Industrial Energy Audit

Background

Apio Inc. is a food processing company in the central coast of California. When Jeff Kraetsch, the Controller, recognized that energy represented a large portion of operational costs at his business he knew he needed help to reduce them. Jeff decided to contact his PG&E representative, Jeremy Howard, looking for help. PG&E assigned kW Engineering to perform an energy audit and help Apio select the best projects to reduce its energy costs under the Large Integrated Audits program.

Energy Audit Process

Peter Pollard, a kW Engineering senior engineer, visited the site and met with staff to assess current operating conditions. The facility recently installed new equipment as a result of steady growth. Approximately two years ago, Apio built a brand new central refrigeration plant that included seven new high quality compressors totalling 2,350 hp. Joe Reynoso, technical manager in charge of all the equipment, was skeptical that money would be found to complete energy-related upgrades.

Pollard interviewed Joe, his staff, and a key contractor to learn details about the various operations at the site. He inspected the facility and its equipment, and installed logging equipment to collect data about how things run. He also analyzed billing data from PG&E, and production data from Apio. From this information Pollard developed a list of possible energy-savings measures, which had some significant savings potential. The site staff met with Pollard to discuss the proposed measures and made adjustments to fully meet facility needs. The team started to get interested as more ideas came forth and they began to see the possibility of significant savings. It also helped that energy savings would justify replacing some older, less-reliable equipment, and provide other non-energy benefits like better lighting and reduced maintenance. Pollard explained that the level of savings would also make most of the projects eligible for large incentives from the utility, PG&E.

Results

kW Engineering’s audit presented measures with total savings potential of $700,000 per year, with incentives bringing the overall simple payback down to about 1 year. Apio got approval from its owners to proceed with almost all measures, in two phases. Phase 1 included a range of measures:

Lighting: All new lighting installed in all plant and warehouse areas. The new premium T8 fluorescent fixtures each turn on only when needed, due to individual occupancy sensors built into each fixture;

Compressed air: With over 300 hp of air compressors at work, accumulator tanks and new larger piping allowed the system setpoint to be reduced which achieved large savings. One compressor received a VFD speed control to operate as an efficient trim unit, while a central control system keeps other units either off or operating flat out for best efficiency. Ventilation added to the compressor room reduced air temperatures for better efficiency and reliability. New controls schedule the compressors to minimize energy use during cleaning and shutdowns;

Refrigeration: Several relatively small, detailed improvements provided large savings. A repair fixed a previously malfunctioning condenser fan VFD. New piping for several evaporators helped them run at a warmer suction. The addition of an efficient VFD control to one 350 hp compressor served the now-expanded high-temperature suction loop. Two compressors serve ice-making systems at a higher head pressure than other compressors, with discharge regulators providing step-down to the common condensers. As a result, a first stage of head pressure control operates remaining compressors at lower, more-efficient head pressures most of the time.